This invention relates to a battery, particularly but not exclusively of the lead acid type.
In a known battery construction the positive and negative plates respectively are electrically connected together and respectively to positive and negative terminals by means of connecting straps. The plates are positioned in a box-like container, usually of moulded plastics material, and a lid is placed on top of the box, the terminals projecting through respective apertures in the lid. The lid is sealed to the box using a suitable cement or by heat-sealing and the terminals are sealed within the respective apertures to prevent unwanted leakage of fluid e.g. acid, fumes or gases such as hydrogen
It is also known to use a settable material such as an epoxy resin to seal the terminals in their respective apertures, but nevertheless leakages can and do occur.
It an object of the present invention to provide an improved construction which does not suffer from or suffers less from this disadvantage.
In accordance with the invention a battery comprises positive and negative plates, two connecting straps, one connected to the positive plates and the other to the negative plates, the plates and straps being enclosed in a box with a lid, two terminals, each one projecting from a respective connecting strap through a respective aperture in the lid, two zones on the underside of the lid each one surrounding one of the two apertures and facing an upper surface of the respective strap, two compressible seals, each one surrounding a respective aperture and being compressibly located between the respective zone and the facing upper surface of the strap, and two spaces, each one being defined around a respective terminal interiorly of the respective aperture, each space containing settable material in a set condition.
Preferably each seal, which may be a sealing ring, is compressed by a predetermined amount and may be retained within a groove which surrounds the respective aperture. The groove may have an overall predetermined depth less than the height of the seal and may be formed either wholly in the zone or wholly in the upper surface of the strap, or partly in the zone and partly in the upper surface of the strap. When the zone is in contact with the upper surface of the strap, the seal is compressed from its natural height to a height equal to the depth of the groove. The amount of compression is thereby predetermined.
Preferably retaining means is provided for each terminal to ensure that the upper surface of the respective strap and the respective zone remain in contact and that the compression of the seal is maintained. The retaining means may comprise a screw-threaded collar positioned on an externally screw-threaded portion of the respective terminal, a lower part of the collar contacting a region of the lid above the aforementioned zone.
At least one channel may be provided for enabling settable material to be fed to the space around each terminal, especially when the retaining means is maintaining the compression of the seal. The channel may be provided in the retaining means and/or in the lid.
The apertures may each be positioned at the base of a respective recess formed in the lid and the retaining means e.g. the collar is positioned wholly within the recess. Settable material may surround the retaining means.
Each terminal may have a lower part which is embedded in the material of the respective strap, the lower part comprising a flanged base portion and a narrower neck portion above the base portion.